Container liquid level indicator



May 3, 1949. H. P. MURPHY 2,468,833

CONTAINER LIQUID LEVEL INDICATOR Filed July 18, 1944 Patented May 3, 1949 UNITED CONTAINER LIQUID LEVEL INDICATOR Harold Purves Murphy, Ridley Park, Pa., assignmto The Electric Storage Battery Company, a I corporation of New Jersey Application July 18, 1944, Serial No.545,521

Claims. (Cl. 116-118) This invention relates to devices for indicating from the outside of an opaque container the height of the liquid contained therein, and has for its object the provision of a device, simple in construction and inexpensive to manufacture, which will indicate positively when the liquid in an opaque container has risen to a predetermined height during a filling operation.

A further object of the invention is to provide such an indicating device which is rugged and without moving parts and not subject to deterioration or accidental injury in service,

Another object is the provision of such a device whose indication can be observed from a point at one side of the container and even below its top.

The invention will be more clearly understood by reference to the following description in connection with the accompanying drawing in which:

Figure 1 is a sectional elevation of a portion of the cover of a storage battery cell equipped with a level indicator embodying features of the invention.

Figure 2 is a similar view showing a modification; and

Figure 3 is an eievational view of the lower end of the device shown in Figs. 1 and 2.

Referring to Fig. 1, I0 is a portion of the cover of a storage battery cell containing electrolyte whose normal level is indicated at I I. The cover is provided with the usual filling opening i2 for the introduction of liquid and with the level indicator of the invention illustrated generally at l3. This indicator comprises a cylindrical rod ll of transparent material such as glass or a synthetic resin such as methyl methacrylate or polystyrene. This rod passes through a threaded opening IS in the cover where it is secured by an externally threaded sleeve l6 attached to the rod H by cement or other suitable means. The sleeve I6 is preferably of opaque material such as hard rubber.

The lower surface I! of the rod H is roughened, frosted or scarified as by etching or grinding and is substantially horizontal and located at the desired maximum level H of the electrolyte.

When the liquid level is below the lower surface I! of the rod [4, light passing down axially through the rod will'be reflected back so that an observer looking down from above will see a bright reflection. When the liquid level rises sufliciently to make contact with the surface ll, light passing down through the rod will no longer be reflected but will be transmitted through the 2 surface 11, which will instantly become dark, indicating that the desired level has been attained.

It is not necessary that the observer's eye be directly above the rod, since the sudden disappearance of illumination is distinctly visible from points above but at some distance from the axis of the rod.

On Fig. 2 is shown a modification in which the cylindrical rod is replaced by a transparent member I8 provided with a curved portion l9 above the cover.

For the curved rod l8, IS, a material of relatively high refractive index is employed and its curvature is such as to cause practically all the light transmitted in either direction to pass around the curve so that the change in illumination resulting from the contact of the liquid with the scarified surface I! will be readily observed from a distance at one side of and even below the top of the cover. The methyl methacrylate resin known by the trade name Lucite is an example of such material, and for "Lucite" the radius of the outer surface of the curved portion l9 should be not less than about three times the diameter of the rod.

I claim: I

1. A device for indicating the liquid level in a container having a cover and containing liquid comprising a rod of transparent material mounted in an opening in the cover, said rod having a rough horizontal surface at its lower end reflecting light from above when out of contact with the liquid and transmitting said light substantially without reflection when in contact with the liquid, said horizontal surface being substantially parallel with the surface of the liquid,

2. A device for indicating the liquid level in a container having a cover and containing liquid comprising a rod of transparent material having a relatively high refractive index and extending down to the desired liquid level and having at its lower end a rough horizontal surface reflecting light from above when out of contact with the liquid and transmitting said light substantially without reflection when in contact with the liquid, said horizontal surface being substantially parallel with the surface of the liquid, said rod curved above the cover substantially out of the vertical.

3. A device for indicating the electrolyte level in a storage battery comprising a rod of transparent material adapted to extend though an opening in the said container and to terminate at approximately the normal electrolyte level, a

3 sealed to the edges of said opening'in said container, and a rough horizontal surface at the lower end of said rod adapted to reflect light when out of contact with the liquid and to transmit light substantially without reflection when in contact with'the liquid, said horizontal surface being substantially parallel with the surface of the liquid, whereby when said roughened surface is covered by, liquid the upper end of said rod darkens noticeably to indicate that the liquid level is at least as high in the container as the lower end of said rod.

4. In a container adapted to receive liquids, a-

device for indicating whether liquid in the contamer is-above or below a predetermined level comprising a rod of transparent material extending into the container and having a portion visible externally oi the container, the portion of the rod within the container terminating at said predetermined level with a surface that transmits light while submerged in liquid and reflects light while not submerged, said surface being substantially parallel to the plane normally assumed by the-liquid, whereby submergence.of the end of the rod is sharply defined.

5. In a container adapted to receive liquids, a

visibility of the liquid level from positions at one side of the container.

. HAROLD PURVES MURPHY.

. REFERENCES CITED The following references are'of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 1,542,183 Steinberg June 16, 1925 1,883,971 Kryzanowsky Oct, 25, 1932 2,290,278 Failla July 21, 1942 

